NP refers to that an telecom user still keeps an original telecom service number under the condition that the telecom user migrates from a permanent address or changes an operator. In other words, the NP requires that the user number remains unchanged permanently. In some regions, the NP, which is taken as a compulsive requirement of telecom supervision, is used for protecting the benefit of weak telecom operators; and part of operators further provide the NP inside an own network to meet the demands of the user who changes the permanent address, so as to reduce the churn rate.
The NP is mainly implemented in a network element that is a CSCF (Call Session Control Function) in the existing IMS network, and specifically, the CSCF acquires callee number information containing NP information of a callee number by an ENUMS (Telephone Number Mapping Server) query; and a calling is routed according to the callee number information. In this way, in a whole calling process, a network element of an IMS is only used for completing routing processing of the calling, and does not judge whether the callee number generates the NP and cannot announce an NP prompt tone to a caller, causing poor user experience.
At present, in order to implement the judgment whether the callee number generates the NP, the IMS network adopts an NP announcement manner as follows: an SCSCF (Serving-CSCF) triggers ENUM to execute an ENUM query to acquire callee number information, a calling, after the ENUM query, is routed to an NPA AS (Number Portability Announcement Application Server), and an NP indicating parameter is contained in a calling request; the NPA AS firstly checks whether a caller has an NP prompt tone announcement attribute after receiving the calling request; under the conditions that the caller has the prompt tone announcement attribute, and the calling request contains the NP indicating parameter, whether a callee generates the NP is judged according to the callee number information and local NP criteria; the NPA AS controls an MRFP (Media Resource Function Processor) to announce the NP prompt tone to the caller when the callee number generates the NP; and after the announcement is ended, the NPA AS sends the calling to the SCSCF, the SCSCF implements the routing of the calling according to route configuration, and the calling is routed to an MGCF (Media Gateway Control Function) for subsequent routing processing.
However, the above NPA manner has greater defects: 1) caller business information needs to be deployed at the NPA AS, and an NPA function can not be provided to a non-NPA AS user; 2) the SCSCF routes all callings to the NPA AS, thereby increasing the performance processing requirements of the SCSCF and the NPA AS to a certain extent; and 3) the requirements of the route configuration of the SCSCF are more complex, thereby being not conductive to subsequent operation and maintenance.